for (var i = 0; i < concepts.length; i++) {
  1 var btn = document.createElement("button");
  2 var attr = document.createTextNode(concepts[i]);
  3 btn.setAttribute("id", concepts[i]);
  4 btn.setAttribute("onClick", "selConcept(this.id)");
  5 btn.appendChild(attr);
  6 document.getElementById("concepts").appendChild(btn);
}